lol. Ya thats how i run my tanks for the most part. On my 16 i got the wrong size light (30 inch coralife 2x65...tank is only 20") sitting right on the top, so it blocks about half the space. Tonight i'm adding 2 baby percs so i'll be putting some egg-crate over the rest.
On my 40 it just has a canopy, and the canopy is completely open on the back. So i just built an extra "wall" on the back opening out of egg-crate.